1. Field of the Invention
This invention is directed to apparatus for separating composite waste material into useful fractions, and especially the recovery of the composite constituents in vehicle tires.
2. Description of the Prior Art
The problems associated with the disposal of composite waste material is the difficulty in recovering the useful fractions in forms that are acceptable for commercial processing. The disposal of vehicle tires is especially troublesome due to the incorporation of steel wire in the rubber. Separation is possible as between steel wire and rubber when an assembly of apparatus is employed for carrying out the necessary steps for progressively separating the steel wire from the enclosing rubber. The apparatus assembled to produce rubber and steel in a continuous process is taught in Miller et al U.S. Pat. No. 4,726,530 of Feb. 23, 1988. A method for crushing waste tires is taught in the Japanese Patent 11,184 of Jan. 27, 1979 issued to Osaka Gar KK, Kobe Steel. This character of separation is only economically possible in a high volume operation which results in having to discard the rubber coated steel wire while keeping the rubber which, for example, can be used as a fuel. The steel when free of rubber represents a high percentage of the tires being processed, and is a valuable asset to be recovered rather than to be discarded.
It is known to provide apparatus for recovering rubber from rubber tires by preparing the tires to cut off the beads where the steel wire is embedded before granulating the rubber. Such apparatus is found in Chryst U.S. Pat. No. 4,422,581 of Dec. 27, 1983 but no provision is made to recover the steel wire which represents about one-third of the body of tires. Another apparatus is disclosed in Mitchell U.S. Pat. No. 4,896,836 of Jan. 30, 1990 wherein the tramp metal is removed magnetically before the rubber material is introduced into a hammer mill, thereby protecting the mill hammers.
Still another type of apparatus is shown in Dorner U.S. Pat. No. 3,923,256 of Dec. 2, 1975 which works up old tires by multi-stage comminution and then sorts the tires into pieces and conveys those pieces to a magnetic separator to remove the steel containing pieces prior to grinding the remainder for reuse. In this patent it is stated that iron-containing pieces of tire sorted by magnetic means represent about 20-30% of the total quantity, and this quantity is disposed of in a manner compatible with the environment on a dump or else is treated in a thermal process.
Scrap tires can be processed to reclaim the rubber and metal in the process set forth in Lovette Jr. U.S. Pat. No. 4,025,990 of May 31, 1977 where recovery of a substantial portion of the valuable components is in a form for secondary use. This recovery is crumb rubber which is used as an additive in asphalt and paving compositions. The metal products can be used in making low grade steel products.